The Interior Department, seeking to curb environmental damage in the nation's coal fields, yesterday proposed new mining regulations designed to halt allegedly widespread misuse of a controversial exemption in a landmark mine-reclamation law.

The provision was intended by Congress to free small "pick-and-shovel" mining operations affecting two acres or less from strict and often costly environmental controls.

Critics, including the Reagan administration's chief surface-mining official, contend that the exemption has been improperly claimed by large and middle-sized mining companies, wildcatters and others. Frequently, the critics note, big companies or subsidiaries employ subcontractors which, in turn, invoke the exemption.

The regulations outlined yesterday would restrict use of the exemption significantly by subcontractors or other small mining companies.

For example, a subcontractor would be barred from claiming the exemption unless the company could show that it was not controlled by the firm that hired it.

Companies would be denied the exemption if they operated several small mines, each affecting less than two acres, in the same region or during the same year. Coal-hauling roads would be included as part of a mine site in computing the two-acre figure.

The rules, drafted by Office of Surface Mining officials after earlier proposals were withdrawn, drew cautious support from environmentalists and congressional aides.

Mark Squillace, an Environmental Policy Institute official, said the regulations appeared "stricter and easier to apply" than previous proposals, though he noted he had not yet examined them. A House staff member said the proposed rules seemed to include "good ideas."

Coal industry officials declined to comment, saying they had not reviewed the regulations. Some industry executives have defended broader interpretations of the two-acre exemption previously, saying it helps provide work for the small mining companies Congress intended to protect. They describe contracting as a longstanding industry practice, contend that environmental damage is minimal at most small mine sites and argue that many of these sites would be unprofitable if stiff environmental controls were imposed.

Much of the controversy about the exemption in the 1977 Surface Mining Control and Reclamation Act has centered on Virginia's Appalachian coal fields. Numerous abuses also have been reported in other states, including Tennessee and Kentucky.

Some of the world's largest coal and energy companies have been linked through subsidiaries and subcontractors to the controversy. Among them are the Pittston Co., a major U.S. coal producer; Sun Company Inc., formerly Sun Oil; W. R. Grace & Co., an international chemicals and natural resources enterprise, and United Coal Co., the largest privately held, independent U.S. coal firm.

Mining companies regulated by the 1977 law are required to take steps to prevent erosion, landslides, water pollution and other harm, and must restore the land to its approximate original contours after the coal has been extracted. The law governs strip mining as well as surface areas affected by underground mines.

The OSM proposals are expected to be published in the Federal Register in about 10 days. A public hearing has not been scheduled. Final regulations are due in March, officials said.

In a related move, Interior also proposed a regulation that would reduce environmental controls on land above underground mines.

Under present rules, all land over deep mine workings is regulated by the 1977 reclamation law. The coal industry has argued that the law should apply only to land that sinks or cracks because of mine operations underneath. The proposed rule would limit environmental controls to land over deep mines where subsidence is expected to occur or is considered possible.